In the field of printing systems, printers may unexpectedly generate small stray marks (or even missing marks) when printing incoming jobs. Depending upon the size of these marks, as well as the nature of the print job, the stray marks may or may not be acceptable to a customer. For example, a small stray mark in one of several thousand copies of a newspaper may be inconsequential, while a small stray mark on a dense technical manual may change the appearance and overall interpretation of an important piece of code or formula. Unfortunately, stray marks can be extremely small (e.g., 1/75th of an inch), which makes manually reviewing a printed job for errors an extremely tedious process. Furthermore, a manual review of the printed pages of an incoming job is unlikely to catch every error. Thus, important print jobs for a customer that are manually reviewed may still be subject to an undesirable level of error when they are delivered.
To address these problems, print shops may include print verification systems. Print verification systems are printing systems that automatically review the output of printers to ensure that they are consistent with quality standards. For example, print verification systems may be used to ensure that no stray marks (or missing marks) appear on printed pages of an incoming job, to ensure that colors printed for a job match their expected hues and saturations, and/or to perform other operations. Print verification systems are particularly useful in ensuring that printed pages meet rigorous quality standards expected for mission critical print jobs.
Currently, print verification systems utilize a printer that receives a print job from a print server. The logical pages of the job are rasterized at the printer in order to generate bitmap versions of each incoming logical page. The rasterized logical pages are then printed at the printer. Furthermore, each rasterized logical page is sent from the printer to a comparison unit, which uses the rasterized logical pages as target images that show an expected printing output. The comparison unit images each printed page and compares it to a corresponding target image from the printer. If there is an error in printing, the comparison unit may then report this result. An example of an existing print verification system is described in U.S. Pat. No. 7,864,349 which is herein incorporated by reference.